Carcinostatic agents such as 5-fluorouracil (5-FU), oxaliplatin, CPT-11 and avastin are now used in various combinations as drug therapy for colorectal cancer. Continuous use for a fixed period of time is indispensable for these carcinostatic agents to exert the effects. However, when these carcinostatic agents are used, various side effects such as fatigue, leucopenia and neurotoxin are exhibited, in addition to digestive symptoms such as nausea, vomiting and diarrhea. Therefore, there are many cases where patients cannot help giving up continuous use of the carcinostatic agent. In the case where the carcinostatic agent cannot be continuously used due to side effects, effects of the carcinostatic agent cannot be exerted, resulting in large disadvantages for patients. That is, in a cancer treatment, countermeasures for side effects of the carcinostatic agent are recognized as urgent issues.
Fucoidan is a generic term of a sulfur-containing polysaccharide containing fucose as a main chain, which exists a lot in seaweeds such as mozuku, root of wakame seaweed (“mekabu”, i.e. sporophyl of wakame seaweed), and is distributed as foods. It has recently been proved that fucoidan inhibits proliferation of cultured gastric cancer cells and reduces toxicity of 5-FU as the carcinostatic agent to normal cells (refer to JP-A-2004-75595). However, there has never been reported whether or not fucoidan can actually reduce toxicity of the carcinostatic agent in clinical trial.    Patent Document 1: JP-A-2004-75595